Corrupted
by Druja
Summary: Frisk had gotten their happy ending. It took them a few tries, and a few deaths, but they had managed. So when it's all forcibly taken away from them again, replaced by a hellish version of their story, they nearly lose all their determination. It takes all they have to keep themselves and Flowey from giving up and letting the twisted monsters take their soul. [Au!Underfell]
1. Chapter 1

**So I also refer to Frisk as a girl in my head, but I'll try to keep it as They/Them for the sake of everyone. So if you see a mention of female pronouns just let me know. I'll try to edit them all out before I post.**

* * *

It was over.

All of it, everything. The deaths and the resets, the fighting and the mercy. They were standing, shivering in anticipation of their friends actions as they watched the sun rise in the far away distance. They were excited, and amazed, and Frisk knew that they would never forget their faces at this moment. They nearly cried in happiness at their friend's reactions, and said yes to being an ambassador so happily it was like they were being asked to be married.

Then, in a rush, everyone ran down the mountain with grins of joy on their faces. Papyrus was first and Sans had followed after, winking at them before leaving.

He was the only one who remembered the other timelines. He was proud of them.

Undyne and Alphys ran after, and Frisk felt accomplished when they saw them hold each other's hand down the mountain. And they almost couldn't help themselves from laughing when Asgore sheepishly ran away from Toriel's heated glare. And when Toriel turned to them, a motherly smile gracing her face, asking them where they would like to go, Frisk knew what their answer was.

They used to live here, but it was never really home. So they had opened their mouth, words of love ready to pour out, when suddenly, a wave of unbearable pain washed through their body, making them cry out from the abruptness of it.

"M-my child?!" Toriel had cried, shocked to see them in pain. She wasn't sure what was happening, but her motherly instincts were in overdrive, and she bent down to Frisk who was now kneeling on the ground, curling into themselves. "Frisk, what's happening? Frisk!? Are you alr- oh... oh my lord..."

There was blood.

And it hurt. It hurt so so much and the world was starting to get blurry. They looked down in wonder and pain at the random wounds that were appearing all over their body, and noticed in a haze that they were all wounds inflicted on them in past timelines; ones that had landed a lethal blow, only they were on a much smaller scale to what they had been, considering they weren't killing Frisk yet. Toriel's burns, Flowey's pellet wounds, bloody spear gashes courtesy of Undyne, a bone or two materializing out of nowhere, wounds from the fight with Asgore whenever they didn't get the timeline right, and numerous cuts and aches and pains from Asriel. They looked at their HP and it looked like it was slowly draining. Frisk was now getting weaker and weaker and could barely hear the sounds of Toriel practically screeching, of frantic calls of her friends who came back up to see what was going on. Frisk felt them surround them, heard them talking, heard someone screaming. And there was just _so much pain_ and then they felt boney hands touch their face and they opened their eyes to see cerulean stare down back at them and they knew that Sans knew what was happening. They barely did, their thoughts overcome with pain, but Sans was there, aware, and unable to do anything and it was _so funny_ because in that last moment before the black that was threatening their vision took over them, their last thought was that they was sorry they couldn't do more to assure him. To comfort all of them.

The change in itself was sudden. The pain was gone, leaving only a slight burning sensation behind and it was dark and cold but Frisk knew where they were. Because they had been here so many times before.

It was the reset screen.

They had died.

And they knew, without any hesitation, that they couldn't reset. Not now. The monsters had their happy ending, even though it ended for them in a strange and painful way. Frisk reflected on that for a moment before shedding a few tears that came to their eyes, selfish thoughts popping up. They didn't _want_ to be dead. They wanted to be with their new family, and friends, and they wanted to be alive and see more of their awestruck expressions and the pain of having to leave their friends behind hit them harder than the wounds did. They _had_ to leave. They couldn't reset. They couldn't do that to them.

And just when they decided that, the resolve firm in their mind, they felt themselves slowly fade away.

It was a weird sensation, they decided. It felt a little like those last moments before you fall asleep, where the only thoughts running through your head are how comfy the bed is and the only thing you feel is this heavy sensation at the back of your eyelids. It was all foggy, full of haze, and as Frisk felt themselves fade away, they smiled softly and-

were abruptly thrust back into darkness.

* * *

Warmth.

That was the first thing they felt. Warmth that caressed their cheek like a gentle hand. Frisk laid there silently, enjoying the comforting feeling, before realizing the other soft tickle on the back of their neck.

Like... flower petals...?

They frowned, awareness reaching up from their mind. Where... where were they? They had a sharp pain all around, but not too terrible for them not to move. What had happened. The last thing they remembered was...

...what was they last thing they remembered?

It was very hard to figure out, the memories just on the tip of their tongue. They were climbing up Mt. Ebott- wait, no... weren't they on _top_ of Mt. Ebott? With friends? Well _that_ didn't make sense; Frisk didn't have many friends up in the Aboveground.

...and since when had they referred to the surface as ithe _Aboveground_? How did they even know they were underground?

 _"I come by everyday to see if anyone has fallen down..."_

Toriel?

 _'Toriel!'_

They jolted up, now fully rehearsed in what had happened just a few minutes ago. The sunrise, the pain, the acceptance, the darkness... Frisk looked around, not missing the yellow flower bed, slightly cracked marble pillars and darkened corners of the room. They had to choke back a sob that rose in their throat.

They had reset.

Which didn't make sense, Frisk pondered after they calmed themselves down; which, admittedly, took longer than they would've liked. They hadn't intended to reset at all- they had let go. Accepted their death. Hadn't they?

 _'And now that I think about it_...' Frisk thought, eyes widened in a sudden realization. _'Why... why didn't I remember it all at first?'_

Every time Frisk had reset, and went back to the beginning, they always remembered what happened right away. And they never confused their memories with the ones they had their first time around- climbing up the mountain. They had almost forgotten everything. _Why had they almost forgotten everything?!_

Frisk took a deep breath. It was going to be okay, they told themselves. They just had to go through it again. Frisk nodded to themselves, standing up and brushing the dirt off their shorts. "I just need to find Sans and As- Flowey." Frisk muttered, remembering that Asriel would have turned back into a flower. The thought upset them. "I need to tell them, and we'll fix it." _'Maybe we could even save Asriel this time.'_

Frisk was filled with Determination- although the prospect of having to die a few more times made it waver ever so slightly...

However, as Frisk went under the arch to the opening where Flowey was, their eyes widened in surprise. Flowey was there, glaring daggers at the young human and showing his most vicious face. It sent chills up their spine.

 **"WHY ARE YOU HERE?"**


	2. Chapter 2

_Previously:_

 _'They jolted up, now fully rehearsed in what had happened just a few minutes ago. The sunrise, the pain, the acceptance, the darkness...'_

 _'They had reset.'_

 _'They had almost forgotten everything. Why had they almost forgotten everything?!'_

 _'"I just need to find Sans and As- Flowey." Frisk muttered, remembering that Asriel would have turned back into a flower. The thought upset them. "I need to tell them, and we'll fix it." 'Maybe we could even save Asriel this time.''_

 _'Flowey was there, glaring daggers at the young human and showing his most vicious face. It sent chills up their spine.'_

 _'"_ _ **WHY ARE YOU HERE?**_ _"'_

* * *

Frisk stared at the flower in shock for a moment. "As- Asriel?" They stammered, their hand over their chest. Honestly, they didn't think they should've been surprised. Asriel had remembered almost all the resets they had done, because he once had the power to do it himself. The fact the prince could remember right now? Frisk couldn't really explain why they were upset. _'Maybe it's because he looks like he wants to hurt me._ ' Frisk thought, slightly scared.

The golden flower's glare grew sharper at the mention of his old name. "Don't call me that!" He snapped, shaking his petaled head wildly as his face morphed back into a regular flower. " _Why_ are you _here_?! Frisk, you were out! _WHY DID YOU RESET?"_

The human was speechless as they stumbled backwards, frightened at his tone. They shook their head vigorously, not trusting their voice at the moment.

The action just got Flowey even more upset.

"You... _you_... do you _not_ understand that _you can't save me?!_ Frisk, the _only thing I wanted_ was for you to get everyone out of the Underground and _leave me alone!_ You stupid human! I'm Flowey again, you've reset... for what purpose? To save me? Damn it _all,_ Frisk! And now... _now you've ruined everything!_ "

Flowey's anger seemed to rapidly dissipate thanks to his venting right before Frisk's eyes, turning into confusion and mourning. He paused for a moment to catch his breath, his golden head lowered to the ground in a position of defeat. Frisk's heart melted as they saw tears dripping from his eyes. "And to think, I thought you were merciful... you couldn't even let me forget it all... you just had to let me remember..."

After a moment to calm their racing heart, Frisk slowly walked up to the flower and sat on their knees, pulling the little flower carefully into their arms. It seemed that he had some resemblance of a soul left to feel strong emotions besides hatred and fear, because he leaned into the gentle hug and sniffed, reminding Frisk of a little child. Which, if they were to be honest with themselves, he was.

"I didn't reset. Or, at least, I didn't mean to." Frisk said quietly as they pulled away. Flowey looked up at them confusedly. "I was up on the surface with everyone, looking at the sunset... when suddenly I just felt this white hot pain..."

Frisk explained to Flowey what had happened, trying to leave as many gory details out as possible. The injuries from past timelines, the acceptance they had of their death (which Flowey frowned at, but didn't comment on), and then waking up again, almost forgetting everything. After explaining, the flower was quiet for a moment before shaking his head.

"I believe you." He said with a sigh. He didn't believe he had a reason not to. He paused before looking away. "Sorry."

Frisk just shook their head in forgiveness, not wanting to use their voice anymore. They rarely used it anyway, it's a miracle they talked as long as they had. Flowey offered a slight smile before gaining a look signaling he was deep in thought.

"Something's obviously really wrong." He stated. Frisk nodded. "The fact that you were hurting from injuries that didn't even technically happen to you... you not being the one to reset? Something's up with the timelines." He looked around, silent for a moment before focusing his attention on Frisk again. He sighed. "Well, I have a feeling that this timeline is going to be playing out a bit different than the rest."

The young human's eyebrows furrowed, and their head tilted. Flowey took this as his sign to continue.

"I mean, if you're not the one resetting... then who is?"

Frisk's eyes widened. Funnily enough, they hadn't really dwelled on that.

"Not only that..." He huffed. "But why did they reset right when the monsters were free? Who could possibly have more determination than you? It still seems to be revolved around you, seeing as how it started with you just arriving in the Underground. What do you think Frisk?"

They nodded in agreement, opening their mouth to quietly contribute before hearing footsteps down the hall, soft and padded feet slapping tile and stone. Frisk smiled in delight.

"It's Mom..." Flowey said, bobbing back and forth uncertainly. His face was scrunched up, and he looked away from the human crouched next to him. "I should probably go, so she doesn't see me."

Frisk couldn't do anything but sadly nod, receiving a small smile from the flower before he dove back into the ground, leaving nothing but a small mound of dirt left in his place. Frisk stood up again, stretching out their legs and facing the door, trying their very best to look curious and slightly scared so Toriel would not suspect that they knew her.

 _'But I do know her... she's my Mom.'_ Frisk thought sadly. _'...and she won't even remember it.'_

The heavy, padded footsteps drew closer. And for some reason, Frisk couldn't help but think that the sound was awfully foreboding.

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 **Awfully short chapter, but I needed a place to end. Next chapter will be filled with the entire story of the Ruins, so I'm planning on it being plenty long. Thanks for the reviews! I appreciate every one of them, especially for helping me find those female pronouns! See any? Let me know! Lord knows I'm terrible at it.**

 **Seeing the reviews filled me with DETERMINATION :3**


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